🛡️ Sentinel: Bound wyoming payload_length to prevent DoS

Co-authored-by: mARTin-B78 <91568406+mARTin-B78@users.noreply.github.com>

linux/blitztext/wakeword.py

@@ -112,6 +112,11 @@ class WakewordListener:
                                 self._handle_detection()
                                 
                             payload_len = msg.get("payload_length", 0)
+
+                            if not isinstance(payload_len, int) or payload_len < 0 or payload_len > 1048576:
+                                logbuffer.log(f"[wakeword] Invalid payload_length: {payload_len}")
+                                break
+
                             if payload_len > 0:
                                 # Consume payload
                                 remaining = payload_len

linux/blitztext/wakeword_bench.py

@@ -322,6 +322,13 @@ def _drain_detections(buf: bytes) -> tuple[bytes, int]:
         except (ValueError, UnicodeDecodeError):
             return rest, found
         plen = msg.get("payload_length", 0) or 0
+        if not isinstance(plen, int):
+            raise ValueError(f"Invalid payload_length type: {type(plen)}")
+        if plen < 0:
+            raise ValueError(f"Negative payload_length: {plen}")
+        if plen > 1048576:  # 1MB limit to prevent DoS via unbounded reads
+            raise ValueError(f"Unreasonably large payload_length: {plen}")
+
         if len(rest) < plen:
             return buf, found  # payload not fully arrived yet; wait for more
         rest = rest[plen:]

linux/tests/test_wakeword_security.py

@@ -0,0 +1,23 @@
+import json
+import pytest
+
+from blitztext.wakeword_bench import _drain_detections
+
+def test_drain_detections_payload_length_validation():
+    # Test massive payload length
+    msg = {"type": "info", "payload_length": 1048577}
+    buf = json.dumps(msg).encode("utf-8") + b"\n"
+    with pytest.raises(ValueError, match="Unreasonably large payload_length"):
+        _drain_detections(buf)
+
+    # Test negative payload length
+    msg = {"type": "info", "payload_length": -1}
+    buf = json.dumps(msg).encode("utf-8") + b"\n"
+    with pytest.raises(ValueError, match="Negative payload_length"):
+        _drain_detections(buf)
+
+    # Test invalid type for payload length
+    msg = {"type": "info", "payload_length": "invalid"}
+    buf = json.dumps(msg).encode("utf-8") + b"\n"
+    with pytest.raises(ValueError, match="Invalid payload_length type"):
+        _drain_detections(buf)